1. Field of the Invention
This invention relates to construction materials and more particularly to such a material comprising a honeycomb core structure made of steel foil.
2. Prior Art
For the maintenance of sufficient mechanical strength at once and light-weight benefit of construction materials over a wide range of application, it has been proposed to use a so called sandwich construction typically in the form of honeycomb cores of aluminum, steel and resin-impregnated paper. As is well known in the art, a plurality of sheets of aluminum foil or paper are coated with an adhesive agent applied in the form of lines extending in parallel spaced-apart relationship and superimposed one upon another with respective adhesive lines shifted a half pitch between adjacent sheets of aluminum or paper to form a block which is then stretched into a honeycomb core structure.
This honeycomb core forming procedure is considered infeasible for a steel sheet or foil matrix which is intrinsically relatively thick and rigid compared to aluminum foil or paper and which is therefore susceptible to buckling upon stretch. In the case of a steel matrix, therefore, a preferred alternative has been to corrugate the matrix with the use of a pair of toothed rolls as shown in FIG. 5 of the accompanying drawings. This corrugated sheet of steel is cut to a desired size as shown in FIG. 6. A plurality of these sheets are superimposed and joined together by brazing with a suitable alloy, or by spot-welding to produce a honeycomb cell structure as shown in FIG. 7.
Such steel honeycomb cores can be applied with relative ease as by welding and finished well as by coating, but the aforesaid corrugation method would be tedious and time-consuming, further involving dimensional irregularities. Conventional steel honeycomb core products have a further drawback in that for example zinc-plating applied for rust-proofing purposes tends to melt away from the surface of the steel foil as the latter is brazed with heat.